LINCOLN, Neb. (Nebraska Forest Service) — Drought is a relatively common occurrence in Nebraska. The further west we go, the drier it is and the greater likelihood of serious drought setting in. In fact, in central and western parts of the state, significant droughts occur on average every 5-7 years. With Nebraska researchers projecting climatic change to increase the frequency and severity of drought cycles, how do we prepare our landscapes for drought tolerance and sustainment when drought sets in?
The good news is that most trees have at least some drought tolerance and are able to survive abnormally dry periods of at least a few weeks. Some species such as juniper, hackberry, bur oak, and gambel oak have remarkable drought tolerance. However, during severe droughts, even long-lived and well-established trees can be significantly stressed. So whenever possible, watering around trees during a drought is generally a good idea. How should trees be prioritized for watering? Here are some suggestions:
- Young and newly planted trees (1-3 years old) should be given the highest priority. Such trees may need to be watered weekly during a drought.
- Established trees more prone to drought stress should have the next priority. In Nebraska, this would include species like red maple, sugar maple, bald cypress, ginkgo, tulip tree, aspen, crabapple, and spruce among others. In a yard with a big bur oak and an old tulip tree, for example, the tulip tree should be watered more.
- Since water runs downhill, trees on drier sites such as the top of slopes or in sandy soils should be prioritized over trees in swales or at the bottom of slopes, where soil moisture will persist longer. Also, south-facing slopes dry out faster than north-facing slopes.
- Trees well adapted to drought should be a lower priority. This would include things like bur oak, honey locust, elms, hackberry, limber pine, and juniper/redcedar among others.
- Don’t just guess at the dryness of the soil but use a probe of some kind like a screwdriver to see how dry it is several inches below the surface. If the soil is still moist, hold off on watering.
How should trees be watered? Ideally, irrigation should be concentrated under the tree's canopy (also referred to as the drip line) long enough so that it soaks into a depth of 8-12” or more. Compared to lawn watering, trees generally require less frequent but deeper watering. For established trees, watering about once a week or every other week should suffice during severe drought. The goal is not to keep the soil saturated all summer but rather just moist enough to keep the tree alive and healthy. One way to think about it is that roughly speaking, Nebraska receives about 1” of rainfall/week on average during the growing season. Mimicking that would be a good way to approach it.
To find out more tips for dealing with drought, visit nfs.unl.edu
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